If $\int \frac{1-x^7}{x\left(1+x^7\right)} d x=a \ln |x|+b \ln \left|x^7+1\right|+C$, then
Answer & explanation
Correct answer: option 3
We have,
$\int \frac{1-x^7}{x\left(1+x^7\right)} d x=a \ln |x|+b \ln \left|x^7+1\right|+C$
Differentiating both sides w.r. to, $x$, we get
$\frac{1-x^7}{x\left(1+x^7\right)}=\frac{a}{x}+7 b \frac{x^6}{x^7+1}$
$\Rightarrow 1-x^7=a\left(1+x^7\right)+7 b x^7 \Rightarrow a=1, b=-\frac{2}{7}$